For task manager to block while trying to End Task Opus implies a low-level problem in something like a hardware driver, filesystem driver, antivirus scanner, or Windows itself.
If the problem was in part of Opus's own code (application level) then task manager would be able to end the process immediately, but if the problem is in some low-level code (kernel level) then the process cannot be stopped until the call into the low-level code returns (which could be never if the low-level code is stuck in a loop).
The Crash, exit or high CPU usage when viewing certain directories guide has suggestions on how to track down which file/folder might be triggering the problem, which may help determine what is wrong.
I agree with Sasa as well: Most registry repair utilities are more likely to break (more) things than fix anything that mattered. (Not always true, but usually.)